Metal forming tools used in fluid forming operations, such as superplastic forming (SPF), quick plastic forming (QPF), and sheet hydroforming, typically include a first portion that defines a fluid pressure chamber and a second portion that defines a forming surface. A metal blank is placed between the first and second portions of the forming tool such that a first side of the blank is in fluid communication with the chamber and a second side of the blank faces the forming surface. Binder surfaces grip the blank along its periphery and provide a seal between the pressure chamber and the blank. Fluid pressure is introduced into the chamber, which acts on the first side of the metal blank, causing the blank to deform so that the second side contacts, and assumes the shape of, the forming surface.
Certain blanks are characterized by regions of different thicknesses. For example, a tailor welded blank includes at least two sheet elements that are welded together at respective edges thereof, forming a weld region. A tailor welded blank is thus characterized by regions of different thicknesses. In order to effect a seal across the tailor welded seam, i.e., at the transition from a first thickness to a second thickness, a tool binder surface must have a step to accommodate the thickness difference. When placing the tailor-welded blank on the forming tool it is essential to precisely locate the seam in the blank to the step in the tool to maintain a pressure-tight seal for the pressure chamber.